I tell off other people's children all the time, if they merit a telling off or their parents are absent/ignoring their appalling behavior.
I don't storm in and rage at them - never ever would I do that. I'm nice, really, but it still gets me into trouble. I say things like "That is the third baby you have pushed over, Gracie - don't push the babies over, it hurts them!"
Large spoilt four year old wails at her mother. Large spoilt child's large spoilt mother comes and mouths off a la Jezza "I'LL DEAL WITH HER, OK?"
"Yes, well", I said "You weren't though, were you? You were drinking tea with your mate while she continues to rugby tackle two year olds and tread on babies. If you were dealing with her, I wouldn't have had to say anything, because you'd have stopped her when she started behaving like a bulldozer, which, by the way, was ten minutes ago."
They retreated back to the tea corner, sat there 'givin' me eeevils' for a few minutes, then stormed out in a high dudgeon. I heard through the grapevine that the group leader rang her and told her off for shouting her mouth off and upsetting the children (which she did) and not supervising her daughter. Well, I say I heard it through the grapevine - the group leader told me.
Said large spoilt child is still large and spoilt though. Can frequently be seen wailing in the playground when games are not going her way and children are not obeying her whims. She's in the same class as Ds2.